Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$86.90	9.837%	$95.4484	$95.45	$95.45	$95.40
Purchase #2	$37.54	8.871%	$40.8702	$40.87	$40.85	$40.90
Purchase #3	$235.85	6.408%	$250.9633	$250.96	$250.95	$251.00
Purchase #4	$69.54	8.636%	$75.5455	$75.55	$75.55	$75.50
Purchase #5	$118.34	7.695%	$127.4463	$127.45	$127.45	$127.40
Purchase #6	$58.65	11.871%	$65.6123	$65.61	$65.60	$65.60
Purchase #7	$142.89	11.850%	$159.8225	$159.82	$159.80	$159.80
7 purchase totals =	$749.71		$815.7085	$815.71	$815.65	$815.60